Victorian Igneous Rocks. 



271 



If vaiiiitiou curves have any real significance, and there seems 

 no doubt that they have, then we must infer that all the rocks whose 

 analyses have been used in the construction of this diagram are 

 genetically related. In this diagram onh- first-class analyses have- 

 been used, and so those of the dacites of Dandenong Ranges and the 

 Black's Spur have been rejected for reason already given. 



Analyses by Dr. Howett of quartz-mica-diorites were not included, 

 as titanium oxide had not been estimated and the methods of analysis 

 as used by him were not as exact as those in use at the present day. 



The molecular ratios for the different oxides present in tlic re- 

 calculated analyses and their totals were determined, and it was 

 found that in this case also the total molecular ratios, or using the 

 term suggested earlier, " the unit molecular concentration," 

 remained approximately constant throughout the differentiation. 

 These molecular ratios are given in Table VI. 



Total 



1.543 1.539 1.539 1.538 1.544 1.541 1.527 1.545 1.539 



Total 



1.542 1.543 1.546 1.543 1.537 1.542 1.541 1.540 1.546 



